Z=10 vs Z=18
Place two elements side by side. Start from atomic number and position, then read the differences in the context of periodic trends rather than as isolated facts.
Z=10
Z=10
Deschide elementul →Z=18
Z=18
Deschide elementul →Mendeleev
Do not compare numbers without asking why they differ. Are the atoms in the same group? The same period? Has a new electron shell appeared? That is where the periodic table becomes an explanation rather than a list.